1. Field of the Invention
The present invention relates to a nonvolatile memory device and a method of fabricating the same. More particularly, the present invention relates to a nonvolatile memory device including a floating gate electrode with an acute-angled tip and a method of fabricating the same.
2. Description of the Related Art
Memory devices are widely used in micro controllers, credit cards, etc. Memory devices may be classified into volatile memory devices and nonvolatile memory devices. In general, volatile memory devices, e.g., DRAM and SRAM, are advantageous with regard to rapid input and output of data, but are disadvantageous because data may be lost after a predetermined time. In general, nonvolatile memory devices, e.g., ROM, are disadvantageous because data input and output may be slow, but are advantageous in that data may be stored for data storage capabilities. Recently, EEPROMs, flash memory devices, etc. are being developed as nonvolatile memory devices that are capable of electrically inputting and outputting data.
EEPROMs or flash memory devices may be classified as a stack gate type and a split gate type. In a memory device of a double split gate type, data is electrically programmed by a Channel Hot Electron Injection method, and erased by an F-N (Fowler-Nordheim) tunneling method. To erase data by the F-N tunneling method, a control gate requires a high voltage. With a demand for devices capable of operating with a reduced driving voltage, a method of forming an acute-angled tip at a floating gate electrode has been studied. However, it is difficult to effectively form a floating gate electrode having a tip with a small inner angle while suppressing side effects like reverse tunneling at the same time.
In the meantime, as the demand for highly integrated chips is increasing, an interval between floating gate electrodes for each cell in the nonvolatile memory device is narrowing. However, as the interval between floating gate electrodes becomes narrow, it is likely that bridges are formed between different cells, leading to reduced device reliability. Therefore, it is necessary to reliably control a position and size of floating gate electrodes.